Traveller rawks, there’s no
doubt about it. And you can get D6s pretty much anywhere. In fact at my
parents’ house, all the board games in the cupboard are pretty well diceless
from constant raids over the years.

But I’m a big fan of percentile
systems, especially the Chaosium system, which I regard as one of the more
elegant and simple mechanic sets in gaming today, especially in regards to
skill advancement. So if you like it as much as I do then here’s how you can
adapt Traveller to a percentile system.

Step 1: Assign base percentages: In blocks of 5% go
through whatever skill list you are using and assign a base skill percentile
rating. This is the basic chance that someone attempting a task with no real
knowledge in that skill has in succeeding. For example, shooting a pistol is
largely point and click (stuff about proper grip, flicking off the safety,
etc., aside), so let’s give Handguns a base value 20%. Physics, however, is
an ornery cuss that needs to be tamed by the mathematically inclined, so
we’ll give it 0%. Actual values should be determined by the referee; in
general, the easier it is for a character to use a skill to good effect with
only a basic orientation, the higher the base percentage should be. The Base
Skill Percentage table shows the values I’ve used when converting from
MegaTraveller.

Step 2: Assign each skill a relevant stat grouping: Each
stat grouping has a primary stat and a secondary stat, representing the
stats most likely to have an impact on the use of the skill. The stat group
provides a single modifier for rolls vs. skills in that group; “primary” and
“secondary” indicate how much influence on the modifier the stat has. See
the Stat Group table for determining which stats apply to which modifiers;
the Base Skill Percentage table also shows the stat groups I’ve used when
converting from MegaTraveller.

Stat Groups

Agility

Used for physically-focused
skills that do not principally rely on fine motor control.
Example skills: Brawling, Blade Combat

Used
for skills with an intellectual
focus
Example skills: Computer, Navigation

Primary Stat:
Education (EDU)

Secondary Stat:
Intelligence (INT)

Manipulation

Used for skills relying
principally on fine
motor control and
coordination
Example skills:
Mechanical, Electronics,

Primary Stat:
Dexterity (DEX)

Secondary Stat:
Intelligence (INT)

Step 3:
Calculate the
character’s stat group
modifiers:
First, determine the
average stat value (A)
for each stat in the
version of
Traveller you are
using. For standard
humans in Classic
Traveller,
MegaTraveller,
and
Marc Miller’s Traveller
(T4), the average stat
value is 7 (2D); for
standard humans in
Traveller: The New Era,
the average stat value
is 5 (2D-2). Note that
if you are attempting to
apply this to races
other than standard
human, you should use
the modified stat rolls
for that race, e.g., for
converting
MegaTraveller
Aslan, the average stat
value for STR is 9
(2D+2)

Next, for each
stat group, calculate
the Primary Stat
Modifier (P) and the
Secondary Stat Modifier
(S): Subtract the
average stat value (A)
calculated above from
the character’s actual
value for the stat.
Preserve the sign; if
the character’s stat is
below the average, it
represents a negative
modification to the base
skill percentage. For
the Primary Stat
Modifier (P), double the
value thus calculated;
for the Secondary Stat
Modifer (S), use the
value thus calculated.
Add P and S; this sum is
the Stat Group Modifier
for that stat group.

For example, the
ubiquitous Terry has a
MegaTraveller UPP
of 7A6864. The Average
stat value is 7 (2D).
Terry’s modifiers would
be as follows:

Add the
Skill Group Modifiers
calculated above to the
base chance percentage
for skills in the
relevant skill group.

Step 4: Convert
current skill levels to
% values and add to base
skill chance (as
modified by the stat
group modifiers):
Use the Skill
Level Modifier table as
shown. Add the indicated
percentage to the
modified base skill
percentage calculated at
the end of step 3.

Skill Level
Modifiers

Skill Level

Percentage
bonus

0

+10%

1

+20%

2

+40%

3

+60%

4

+70%

5

+80%

6

+90%

Note: For each level beyond 6 add an additional 5% (although few referees would allow skills to get this high).

‘Serves As’ Skills: If a character has a skill that ‘serves as’ other skills, treat each skill in the combination separately. For example, in MegaTraveller, Liaison serves as Admin – 1 and Streetwise – 1. A character with a skill of Liaison-3 would add 60% to their Liaison percentage value and 40% each to their Admin and Streetwise percentage values (as though they had Admin-2 and Streetwise-2).

Example: Terry from the above example has Carousing-1. The referee (me in this case) decides this is an everyman skill and gives it a base value of 20%. I assigned Charm as the appropriate skill grouping. Terry’s modified chance looks like this
20% (Base Skill Percentage for Carousing) –5% (Charm modifier) + 20% (skill level 1) = 35%

Base Skill Percentages and Skill Groups

Skill

Base Skill %

Skill Group

Skill

Base Skill %

Skill Group

Administration

10

Charm

Intrusion

0

Manipulation

Artisan

10

Manipulation

Jack-of-all-trades

See note 1

Axe

10

Agility

Jet-propelled Aircraft

0

Manipulation

Battle Dress

0

Manipulation

Large Blade

10

Agility

Biology

0

Knowledge

Large Watercraft

5

Knowledge

Blowgun

5

Manipulation

Laser Weapons

5; 20 if tech 9+

Manipulation

Bola

0

Manipulation

Leader

15

Charm

Boomerang

0

Manipulation

Legal

5

Knowledge

Bow

10

Agility

Liaison

10

Charm

Brawling

20

Agility

Lighter-than-air Craft

0

Manipulation

Bribery

10

Charm

Linguistics (see note 2)

5

Knowledge

Broker

10

Charm

Mass Driver

0

Manipulation

Carousing

20

Charm

Mechanical

10

Manipulation

Chemistry

0

Knowledge

Medical

5

Knowledge

Combat Engineering

0

Knowledge

Meson Guns

0

Manipulation

Combat Rifleman

10

Manipulation

Mortars and Howitzers

0

Manipulation

Communications

10

Knowledge

Naval Architect

0

Knowledge

Computer

0; 20 if tech 9+

Knowledge

Navigation

0

Knowledge

Crossbow

10

Manipulation

Persuasion

10

Charm

Cudgel

20

Agility

Physics

0

Knowledge

Demolition

0

Manipulation

Pilot

0

Manipulation

Disguise

5

Charm

Plasma Gun

0

Manipulation

Early Firearms

5

Manipulation

Polearm

5

Agility

Electronics

5

Manipulation

Propeller-driven Aircraft

0

Manipulation

Energy Weapons

5

Manipulation

Prospecting

0

Knowledge

Engineering

0

Knowledge

Reconnaissance

10

Knowledge

Equestrian

10

Agility

Recruiting

5

Charm

Fleet Tactics

0

Knowledge

Rifleman

20

Manipulation

Foil

10

Agility

Robot Operations

0; 10 if tech A+

Knowledge

Forensic

0

Knowledge

Robotics

0

Knowledge

Forgery

0

Manipulation

Screens

0

Manipulation

Forward Observer

0

Knowledge

Sensor Operations

0

Knowledge

Fusion Gun

0

Manipulation

Ship Tactics

0

Knowledge

Gambling

10

Charm

Ship's Boat

0

Manipulation

Genetics

0

Knowledge

Sling

0

Manipulation

Grav Belt

0; 5 if tech B+

Manipulation

Small Blade

15

Agility

Grav Vehicle

0; 20 if tech 9+

Manipulation

Small Watercraft

0; 5 if hydro 4+

Manipulation

Gravitics

0

Knowledge

Spinal Weapons

0

Manipulation

Guard/Hunting Beasts

5

Charm

Stealth

15

Agility

Handgun

20

Manipulation

Steward

20

Charm

Heavy Weapons

5

Manipulation

Streetwise

5

Charm

Helicopter

0

Manipulation

Submachinegun

10

Manipulation

Herding

5

Charm

Survey

0

Knowledge

High Energy Weapons

0

Manipulation

Survival

0; 10 if atmos 4-9

Knowledge

High-G Environment

0

Agility

Tactics

5

Knowledge

History

15

Knowledge

Tracked Vehicle

5

Manipulation

Hovercraft

0

Manipulation

Trader

5

Charm

Hunting

5

Knowledge

Turret Weapons

5

Manipulation

Instruction

10

Charm

Vacc Suit

0

Agility

Interrogation

5

Charm

Wheeled Vehicle

0; 10 if tech 4-8

Manipulation

Interview

10

Charm

Zero-G Environment

10

Agility

Note 1: J-O-T is harder to convert. I recommend the following. Each session the character is allowed (J-O-T level) automatic re-tries at a failed skill roll without having to make a determination check.

Note 2: For each level of Linguistics the character receives their EDU % stat value in a specific language, e.g., Terry has Linguistics-2 and can speak Vilani and Gvegh. His EDU % value is 45%. He gets 45% in Vilani and 45% in Gvegh. From this point he advances in those languages normally. Once converted, Linguistics no longer offers automatic language ability. Instead, if a character’s Linguistics skill % is higher than a language %, they double any skill advancement rolls.

Skill Resolution: It’s a simple matter of if a percentile dice roll is equal to or less than the character’s percent chance of success as calculated above, they succeed. This assumes a difficult task. For easier tasks modify the chance by blocks of 10% upward. For example, a routine task might be +20; a simple task might be +40%. For stupidly harder tasks, modify in blocks downward, e.g., a formidable task might be –20%.

Experience: This is the best part. The Traveller experience systems were always pretty harsh on the old character. And, let’s face it, players love nothing more than advancing their character’s skills. While we mortals spend our leisure time watching TV, or gaming, our fictional counterparts are hitting the gym or the books, watching what they eat, etc.

Again, borrowed from Chaosium, experience is simple. If a character succeeds at a skill during a game session that the referee feels advanced the story and so forth, they can check it. At the end of the session they roll percentile dice. If the result is equal or exceeds their current skill then increase the skill percentage chance value by D10/2 (round down; range is 0-5%). The beauty is that probability means that higher skill percentage chances will be much harder to obtain.

Training: Once a PC spends (current skill %) hours dedicated to training in a specific skill they can make a roll vs. INT. If they succeed, they get a skill check, as for experience. The referee is free to modify the roll for access to instructors, training aides, conditions or study etc.

Statistic percentile checks: Naturally, if you’ve gone and applied the above, you'll want to do the same for stat checks.

For Classic Traveller, MegaTraveller, and Marc Miller’s Traveller, where the average stat value is 7, add 3 and multiply the result by 5. e.g., 7+3 is 10; 10 × 5 is 50%. For Traveller: The New Era, where the average is 5, multiply by 10, e.g., 6 × 10 is 60%.

Advancing Stats: If a character checks a stat, make the experience roll as normal, adding any percentage boost to the stat percentile value. When their stat percentile value reaches a multiple of 5, increase the actual stat value by 1 point.

Example: Terry has an INT of 8, with a percentile value of 55%. He manages to get 3% added to his INT percentile chance. So, his stat now reads INT 8 (58%). When his INT percentile chance gets to 60%+, he can boost the actual value of his INT from 8 to 9 (his stat would then read INT 9 (60%)).